The present invention relates to an optical pickup device-holding container, and more particularly to a holding container used for an optical pickup device adapted to irradiate an optical recording medium such as a compact disk with a light beam, receive reflected light from a recording surface to give an optical signal corresponding to a change in the reflected state of the light beam on the recording surface, and convert the optical signal into an electrical signal to conduct recording or reproduction. The present invention also relates to an optical pickup device in which components such as a light source, an objective lens and a light-receiving part are held in the holding container.
In recent years, optical recording mediums (optical disks) such as compact disks (CD), digital video disks (DVD), laser disks (LD) and mini disks (MD) have been widely used as various recording mediums, since they have a high memory density and a great memory capacity and are easy to random access. The recording and/or reproduction of information is conducted by irradiating a surface (recording surface) of an optical recording medium with a light beam.
An optical pickup device is used to irradiate the recording surface of the optical recording medium with the light beam for recording/reproduction. The optical pickup device is generally equipped with at least a light source, an objective lens and a light-receiving part, and those of various systems and types have been known (for example, Japanese Patent Application Laid-Open Nos. 315402/1996, 315406/1996, 321067/1996 and 321068/1996).
An example of the optical pickup device is illustrated in FIG. 1. In the optical pickup device illustrated in FIG. 1, a laser beam outputted from a semiconductor laser (light source) 1 is focused on a recording surface 8 of an optical disk 7 by an objective lens 3 through a plane half mirror (beam splitting part) 2 and a collimator lens 4. Reflected light (return light) from the recording surface is struck on a four-split photo diode (light-receiving part) 5 through the objective lens 3, the collimator lens 4 and the plane half mirror 2 to give data signals and error signals (focus error signals and tracking error signals). The objective lens 3 is moved vertically and laterally according to the error signals to conduct focus control and tracking control.
Such components as described above in the optical pickup device are generally held in a holding container 6. A metal-made holding container has heretofore been used in the optical pickup device. However, the holding container is in an extremely complicated form, since the components must be installed therein. Therefore, extremely difficult processing has been required in order to produce a metal-made holding container.
When a synthetic resin is used in place of a metal, a holding container can be easily produced by, for example, injection molding even when it has a complicated form. However, the holding container made of the synthetic resin is poor in thermal conductibility and hence involves a problem that it tends to be deformed by heat generated from the semiconductor laser and temperature rise at the light-receiving part of signal light. When the holding container is deformed even a little, there arises a problem that positions of the individual components held therein vary to cause the slippage of an optical axis. Besides, the form of a spot of the light beam on the recording surface of the recording medium is distorted by the temperature rise, and moreover the form of a light spot at the light-receiving part is also distorted, so that stable recording and reproduction become difficult.
Since a digital video disk (DVD) in particular is required to have interchangeability with other optical disks, and signals are stored in its recording surfaces different in depth from each other, it has been necessary to extremely strictly control the positions of the individual components held in the holding container in order to conduct stable recording and reproduction using such a disk. This demand is extremely strong in the conventional pickup devices for optical disks, particularly, digital video disks, and so the use of a holding container made of a synthetic resin, which tends to cause heat accumulation and heat distortion, has been difficult.
It is an object of the present invention to provide an optical pickup device-holding container made of a synthetic resin, which is excellent in heat resistance, dimensional stability, heat distortion resistance and thermal conductibility. A particular object of the present invention is to provide an optical pickup device-holding container suitable for digital video disks.
Another object of the present invention is to provide an optical pickup device in which components such as a light source, an objective lens and a light-receiving part are held in a holding container made of a synthetic resin, which is excellent in heat resistance, dimensional stability, heat distortion resistance and thermal conductibility.
The present inventors have carried out an extensive investigation with a view toward overcoming the above-described problems involved in the prior art. As a result, it has been found that when a resin composition comprising a poly(arylene sulfide) and an inorganic filler and having a thermal conductivity of at least 1 W/mK is used to produce an optical pickup device-holding container, a holding container excellent in heat resistance, dimensional stability, heat distortion resistance and thermal conductibility can be provided, and stable recording and reproduction can be conducted by an optical pickup device obtained by installing the components thereof in this holding container. The present invention has been led to completion on the basis of these findings.
According to the present invention, there is thus provided an optical pickup device-holding container which is formed from a resin composition comprising a poly(arylene sulfide) (A) and an inorganic filler (B) and having a thermal conductivity of at least 1 W/mK.
According to the present invention, there is also provided an optical pickup device, in which at least a light source, an objective lens and a light-receiving part are held in a holding container, wherein the holding container is formed from the above-described resin composition.
According to the present invention, there are further provided the following preferred embodiments:
1. The optical pickup device-holding container, wherein the resin composition comprises, per 100 parts by weight of the poly(arylene sulfide) (A), 50 to 300 parts by weight of metal oxide powder (B1) and 20 to 300 parts by weight of a fibrous filler (B2) as the inorganic filler (B).
2. The optical pickup device-holding container, wherein the metal oxide powder (B1) is at least one selected from the group consisting of iron oxide and aluminum oxide.
3. The optical pickup device-holding container, wherein the fibrous filler (B2) is at least one selected from the group consisting of glass fibers, carbon fibers, wollastonite, potassium titanate and aluminum borate.
4. The optical pickup device-holding container, wherein the poly(arylene sulfide) is poly(phenylene sulfide).
5. An optical pickup device equipped with the holding container according to any one of the above items 1 to 5.